1. The Future: Is Ribavirin Still Useful? David Nelson, MD Professor of Medicine, Microbiology, and Molecular Genetics Associate Dean, Clinical Research and Training Director, Clinical and Translational Science Institute University of Florida 5 th Paris Hepatitis Conference

2. History of Ribavirin 1970: first synthesized at ICN Pharmaceuticals 1972: ribavirin active against a variety of RNA viruses (including flavivirus) – Failed FDA approval for influenza 1980: approved indication in inhalant form for RSV 1998: oral ribavirin approved as part of a combination treatment (with interferon) for hepatitis C – Improved SVR rates by 20-30% Prevention of relapse

3. Adapted from US Food and Drug Administration, Antiviral Drugs Advisory Committee Meeting, April 27-28, 2011, Silver Spring MD. SVR (%) IFN 6m Peg-IFN/ RBV 12m IFN 12m IFN/RBV 12m Peg-IFN 12m 2001 1998 2011 Standard Interferon Ribavirin Peginterferon 1991 Direct Acting Antivirals Peg-IFN/ RBV/ DAA IFN/RBV 6m Interferon-Based Therapy Critical Role for Ribavirin in HCV Therapy

4. Proposed mechanisms of action for ribavirin against HCV include Direct effect against the HCV RNA dependent RNA polymerase Induction of mis-incorporation of nucleotides leading to lethal mutagenesis Depletion of intracellular pools via inhibition of inosine monophosphate dehydrogenase Alteration in the cytokine balance between a Th2 profile (anti-inflammatory) to a Th1 profile (pro-inflammatory) Potentiating the effect of interferon via up-regulation of genes involved in interferon signalling Clark V, Nelson DR. Liver Int 2012; 32:103-7

5. Perspectives on Ribavirin Role in DAA Combinations Pros – It works: leads to higher SVR across all trials to date Cons – Very “weak” antiviral – Lack of understanding MOA: difficult to predict best combination with DAA – Adverse events Hemolytic anemia (monotherapy trials) – Mean hgb reduction > 2gms by week 4 – 20% pts have > 4 gm drop Teratogen Pill burden and bid dosing

6. In-Vitro Prediction of RBV + DAAs Protease inhibitors 1 – PI + RBV = additive antiviral activity – PI + PEG/RBV = synergistic effect Reduce emergence of drug resistant variants 1. Hofmann WP, et al. Antivir Ther 2011; 16:695-704

7. 7 PROVE-2 1 PROVE-3 2 SVR (%) 0 20 40 60 80 100 PR 48 wk (no lead-in) (n = 16) B + P + low-dose R (48 wk) (n = 59) SPRINT-1 3 36%50%36% 24%53% 60% Ribavirin Is Critical for Protease Inhibitor Combination Therapy: Phase 2 Trials Dosages not consistent between above studies. Abbreviations: B, boceprevir; P, peg-IFN  -2a and -2b; R, ribavirin; T, telaprevir. Hezode C et al N Engl J Med 2009;360:1839.; McHutchinson JG, et al. N Engl J Med 2010;362:1292; Kwo PY et al. Lancet 2010;376:705 T 12 wk + PR 12 wk (n = 82) T 12 wk + P 12 wk (n = 78) T 24 wk + PR 48 wk (n = 113) T 24 wk + P 24 wk (n = 111) PROVE IIPROVE IIISPRINT-1

8. Impact of RBV on Virologic Breakthrough Role of Viral Subtype Patients with confirmed virologic breakthrough (%) T12/PR24 0 10 20 30 40 50 T24/P24 (no RBV) T24/PR48 Genotype 1a Genotype 1b 2 PR48 (control) 1 10 2 3 23 6 McHutchison JG, et al. Hepatology. 2009;50:334A-335A. (PROVE III)

9. Summary Patients that did not receive RBV in the PROVE trials and those with low dose RBV in the SPRINT-1 trial had – Increased viral breakthrough – Higher relapse rates – Lower SVR Standard dose RBV is required to optimize response to first generation PIs

10. Balapiravir (RG1626): RBV provides significant antiviral activity with IFN + Nuc Treatment ArmMean Reduction in HCV RNA Level from Baseline log 10 IU/mL Week 1Week 2Week 3Week 4 PEG-IFN + RG1626 2.43.13.93.6 PEG-IFN + RG1626 + RBV 3.34.65.15.2 PEG-IFN + RBV1.11.62.12.4 Nelson DR et al. Ann Hepatol 2012; 11(1):15-31

11. Role of Ribavirin Interferon-free Regimens

12. Day Median HCV RNA (IU/ml) Log 10 0 1 3 2 4 7 14 2128 6 5 7 GS-9256: protease inhibitor GS-9190: polymerase inhibitor GS-9256 + GS-9190 (n = 15) GS-9256 + GS-9190 + RBV (n = 13) GS-9256 + GS-9190 + PEG IFN/RBV (n = 3) Breakthrough Ribavirin Reduces Viral Breakthrough In Protease + Polymerase Combination Zeuzem S, et al. Hepatology. 2010;52:Abstract LB-1.

13. ZENITH: VX-222 + Telaprevir ± PegIFN/ RBV in Genotype 1 Treatment-Naive Pts VX-222, NS5B nonnucleoside, polymerase inhibitor 2-drug arms terminated due high rates (>25%) of on-treatment breakthrough – 12 vBT (11 G1a and 1G1b) – new arm added: VX-222 400 mg QD + telaprevir 1125 mg BID + RBV. * † PegIFN 180 µg/wk + weight-based RBV 1000-1200 mg/day. Treatment-naive patients with chronic genotype 1 HCV infection* (N = 106) VX-222 400 mg BID + Telaprevir 1125 mg BID (n = 29) VX-222 100 mg BID + Telaprevir 1125 mg BID + PR † (n = 29) VX-222 400 mg BID + Telaprevir 1125 mg BID + PR † (n = 30) Wk 12 VX-222 100 mg BID + Telaprevir 1125 mg BID (n = 18) Wk 36 ‡ Wk 24 Nelson DR, et al. AASLD 2011. Abstract LB-14. PR for 12 wks if HCV RNA detectable at Wks 2 or 8 † Stop tx if HCV RNA undetectable at Wks 2 and 8 †

14. HCV Gen 1b Can Be Cured Without IFN or RBV BMS-790052 (NS5A) + BMS-650032 (NS3) 1. Lok A, et al. EASL 2011. Abstract 1356. 2. Chayama K, et al. AASLD 2011. Abstract LB-4. 100 80 60 40 20 0 36 SVR24 (%) 90 90 † N/A US Study [1] AASLD 2011: Japan Study (N = 10) [2] 9/10 n/N = 4/11 9/10 BMS-790052 60 mg QD + BMS-650032 600 mg BID + PEG-IFN/RBV A n=11 B n=10 BMS-790052 60 mg QD + BMS-650032 200 mg BID BMS-790052 60 mg QD + BMS-650032 600 mg BID Expansion A1 n=10 (GT-1b) weeks 024

15. 8 PSI-7977 400 mg + PegIFN/RBV Week PSI-7977 400 mg + RBV 12 PSI + R 12 weeks n=10 PSI + PR 12 weeks n=10 4 PSI-7977 400 mg + RBV PSI-7977 400 mg + PegIFN/RBV PSI + PR 8 weeks n=10 PSI + PR 4 weeks n=10 PSI-7977 400 mg + RBV 15 ELECTRON PSI-7977 + RBV (GT-2/3) Gane EJ, et al. AASLD 2011. Abstract 34 PSI-7977 400 mg PSI 12 weeks n=10

16. PSI-7977 ELECTRON What is the role of Ribavirin? Assay LLOD 15 IU/mL PSI-7977/RBV Combined IFN Arms Time (Days) 027142128 Mean HCV RNA (Log 10 IU/mL) 0 1 2 3 4 5 6 7 PSI-7977 Monotherapy

17. PSI-7977 + RBV (GT-2/3) Ribivirin Prevents relapse Gane EJ, et al. AASLD 2011. Abstract 34 100 60

18. ELECTRON: Anemia RBV Impact on Hemoglobin with IFN-free PSI-7977/RBV PSI-7977 + RBV

19. Alisporivir 600 mg BID + RBV Alisporivir 600 mg BID + PegIFN Week Alisporivir 800 mg QD + RBV* 24 ALV1000 n=83 ALV-P n=39 1 Alisporivir 600 mg BID Alisporivir 600 mg BID + RBV ALV800R n=94 ALV600R n=84 Alisporivir 600 mg QD + RBV* 19 Alisporivir (GT-2/3) Pawlotsky JM, et al. AASLD 2011. Abstract LB-11 PegIFN/RBV PR n=40 VITAL-1: phase IIb trial of alisporivir in treatment-naïve HCV GT-2 or GT-3 patients Alisporivir 1000 mg QD* Alisporivir 600 mg QD + PegIFN* *Patients with HCV RNA ≥25 IU/mL at Week 4 received alisporivir 600 mg QD + PegIFN/RBV from Week 6 until Week 24

20. 20 Alisporivir in Genotyope 2/3 Pawlotsky JM, et al. AASLD 2011. Abstract LB-11

21. Conclusions The question of the role of RBV remains as real today as it was two decades ago! Critical role for RBV in combination with DAAs for both IFN- containing and IFN-sparing regimens – Leads to higher SVR Additive antiviral activity – Accelerates second slope of viral decline Prevents relapse and viral breakthrough RBV-free regimens more likely with potent and high-genetic barrier regimens and subtype (1b >1a)